Neurons in the dorsal region of the medial superior temporal area (MSTd) of monkey extrastriate cortex have previously been shown to respond to the expanding radial motion that occurs as an observer moves through the environment. In previous experiments, the MSTd neurons have been shown to respond to radial and circular motion when the center of that motion was in the middle of the visual field. Different directions of observer motion e accompanied by centers of motion located in different areas of the visual field, and in our current experiments we tested to see whether MSTd neurons responded best when centers of motion were located in different parts of the field. About 90 percent of the 245 neurons studied responded differently to at least one stimulus with a shifted center of motion as compared with those positioned in the middle of the visual field. The preferred centers of motion were always limited to one area of the visual field for a given cell, and all parts of the visual field were represented. There was a preference among the sample of neurons for centers of motion located closer to the middle of the visual field, and neurons preferring th part of the field also responded to centers of motion over a more limited region of the field. Based on these observations, we suggest that each of the MSTd neurons has a center of motion field with a gradient of preferred centers of motion and that there is an orderly arrangement of these neurons with each region of the visual field being represented by a set of neurons. This neuronal organization creates the potential for graded responses from individual neurons for different directions of heading as an observer moves through the environment.